1. Field of the Invention
The present invention concerns a progressive ophthalmic lens and is more particularly concerned with the configuration of the progressive area of this type of lens.
2. Description of the Prior Art
Progressive ophthalmic lenses designed to compensate for accommodation defects of the crystalline lens comprise in the known way a substantially constant power first area for far vision, a substantially constant power second area for near vision and between these two areas a third area of progressively varying focal power merging with the first two areas continuously.
The various known progressive lenses represent a compromise between various parameters, the most important of which include the length and the law of progression, the distribution of powers, the reduction of distortion and the adaptation to binocular vision.
However, none of the known lenses attempts to optimize the progression corridor that is formed by the central part of the progressive area to either side of the main progression meridian, in other words to confer on this progression corridor a width and optical characteristics such that the person wearing the lenses can use any area within the corridor for continuous, or in other words permanent viewing of objects situated at a distance intermediate far vision and near vision.
The present invention is directed to a progressive ophthalmic lens meeting this condition in particular.